1. Field of the Invention
This invention relates to a method of SO.sub.2 removal and recovery as a sulfite salt from ore smelter and like exhaust gases, by refrigeration and water scrubbing of the cooled exhaust gases, the SO.sub.2 removal being in liquid phase as a solute in the scrubbing water.
2. Description of the Prior Art
Hasche U.S. Pat. No. 1,810,312 discloses a system for recovery of sulfur dioxide from smelter furnace gases by refrigeration and liquefaction under pressure. The Hasche system separates sulfur dioxide from the smelter gaseous effluent by anhydrous liquefaction of the sulfur dioxide at about -70.degree. C. and about 15 atmospheres pressure, the use of pressurization in the system being to reduce the refrigeration requirement dictated by the necessity for anhydrous sulfur dioxide liquefaction. In contrast, the treatment process of the present invention operates at substantially atmospheric pressure and the sulfur dioxide present in the smelter furnace products of combustion is removed in the form of sulphurous acid, i.e. by taking advantage of the water solubility of sulfur dioxide in the refrigerated scrubbing water. In the Hasche system the water vapor is removed prior to the sulfur dioxide liquefaction, ie.e. the sulfur dioxide in liquid phase appears in this system under essentially anhydrous conditions because the refrigeration necessary for the sulfur dioxide liquefaction is at a temperature (-70.degree. C.) far below the freezing temperature of water.